Photo-electric tube



March 13, 1934. s. WEIN PHOTO-ELECTRIC TUBE Filed Jan. 28, 1950 INV AWW2 BY A TTORNE Y.

Patented Mar. 13, 1934 UNITED STATES PHOTO-ELECTRIC TUBE Samuel Wein,New York, N. Y., assignor to Radiovision Corporation, New York, N. Y., acorporation of New York Application January 28, 1930, Serial No. 423,984

1 Claim.

This invention relates to photoelectric tubes.

The invention has for its object the construction of a photoelectrictube which can be readily duplicated, and which is simple tomanufacture.

The conventional photoelectric tube, 1. e., in which an alkali metal isdeposited on the inner wall of the glass container is difficult tomanufacture as great skill and care must be exercised to distill thealkali metal on the inner surface of the glass. Tubes so constructed areseldom alike, irrespective of the fact that a plurality of these tubesare made simultaneously and under the same conditions. The costs ofmanufacturing such tubes are high, because not all the tubes made can beused.

By the present invention, photoelectric tubes are easier to manufacture,and the tubes may readily be reproduced having the same characteristics.The constructional design permits of manufacture by automatic machinery,in the same fashion as is done with incandescent lamps, radio and othertubes.

In the accompanying drawing:--

Figure l is a rear view, partly in section, of a photoelectric tubeembodying the invention, and

Figure 2 is a front view showing the arrangement of the parts of thephotoelectric tube, of Figure 1, with the container omitted.

The numeral 1 denotes a container preferably a glass vessel, such as theordinary tube. It is obvious of course that quartz, or other transparentmaterial, may be used.

The cathode 2 may take the form of a metal box, on to which is depositeda thin and homogeneous film of any of the oxides of the alkali metals.This film is indicated at 3. Many metals may be used for the box and thefilm, depending upon the results desired.

The cathode may be of any shape or form, such as a tube, as long as itserves to cut off light from the heater element or filament, ashereinafter referred to.

The outer surface of the cathode may be oxidized in any convenientmanner, either before being mounted in the container, or after beingassembled. Any suitable method of depositing the sensitive film thereonmay be used and several methods are known.

The cathode 2 may be made of one piece, or of several piecesconveniently folded over and spot welded as indicated at 4. If metaltubes are used, there is no need of folding the metal over, a top andbottom cap being applied to same.

8 is a bottom plate with a slot therein, as shown in Figure 1, so as topermit the filament terminals to enter the cavity within the cathode.This bottom plate may be made of the same material as the cathode 2, orit may be made of a refractory material or glass.

The heavy wires 9 are supports to hold up the cathode 2 and one of themcontinues through the press or seal of the tube and connects to one ofthe circuit terminals thereof.

Inside of the cathode 2 is placed filament 7. This filament may be madeof platinum or nickel with a film of alkali metal oxide thereon, or itmay be made of thoriated tungsten, molybdenum, etc.

The heater element 7 may be of any suitable type, and need notnecessarily be a filament which is shown merely by way of illustration.

The filament is supported by spring 6, which is intended to take up thefilament 7 during stretching. Spring 6 is held in position by theinsulator 5 mounted upon the cathode.

By the construction just described, light from the filament or heater 7is prevented from impinging upon the sensitive surface 3 of the cathode.Such light would interfere with the operation of the tube, for obviousreasons.

The filament '7 may be used in the production of the metal oxide, as forinstance by passing a potential through same thereby causing the metalbox to become hot, and if oxygen at a low pressure is admitted to theglass container, the metal surface or alkali metal film on the cathodewill be converted into the corresponding oxide.

If a potential is passed between the cathode 2 and the anode grid orcollector 10, while element 2 is hot (or cold) in the presence of a lowpressure in oxygen, it will convert the metal film 3 into thecorresponding oxide. This potential may be either D. C. or A. C. ofsuitable voltage.

After the metal film constituting the sensitive surface 3 has beenformed, the glass vessel is highly evacuated and sealed off. The tube soformed is now mounted on the usual support or base and provided with thenecessary terminals (not shown) for the filament, anode and cathode.

Noble or inert gases may be incorporated in the glass container prior toits being sealed off.

The filament 7 may be used as a means to bombard the cathode 2, withoutactually heating the same, the heating effect in this case being ofsecondary consideration as the tube will function by bombardment onlyunder certain conditions.

Many modifications of this photoelectric tube construction are possible,without however departing from the appended claim.

I claim: 7

A photoelectric tube comprising an envelope housing a hollow cathodecoated upon the exterior surface with a photo-sensitive coating of analkali-metal oxide and having within a heater element therefor, and aforaminous anode mounted in front of said cathode.

SAMUEL WEIN.

